Verifying in the mongod client

my mind before hitting the head against wall:

It seems little weird to me. Since it is a nosql mapper or what? I come from django experience, I expected the field has to be updated even the default value is given to be updated for the existing rows. But it doesn’t happen. So, what happens is, If the value of the new field changed from the default value(`false` here) to the some other value(`true`) then the update reflects successfully.

There is a solution for every problem.
Yes. This is an obvious statement which I realized after a while hitting my head against the wall.
if you inherit from `DynamicDocument` for mongoengine odm. You will get the clear solution. It does the job.
The learn happens after this post gets published :)

Erlang day1:

Erlang shell an introduction

How to use the erlang shell?

few basic data structure tricks

Erlang shell an introduction:

In order to get your erlang shell,you have to install the erlang OTP for your platform(Windows/Linux).
Once installed erlang software, you can type erl to launch the shell.
In erl you can do the experiments in erlang.

watch the screen & read the below marks:

Few things keep remember:

The new values can’t be assigned to the bounded varialbes.Use always a unbound variable to store the value.Varialbes starts with caps(i.e Var)._ is always used to unregister the value.The value will be omitted if it is assigned to the underscore.

Data structures are atoms, tuple, list.

tuple: It is represented by {}. e.g {1,2,3,4}.

atom: This is just a variable which is used name the data to match the pattern.

eg. {person, Name} = {person, "navaneethan"}.

in this above example two tuples are matched with help of atom person, so the variable Name will be bounded to the value navaneethan.Finally, this pattern match is successful.

an intro to Erlang:

I have started Erlang last weekend.Few things will amaze you if you start following it.You would get inspired of it’s powerful features.I would like to share with you my thoughts also what I learned in this one day.

Erlang creations:

Using erlang, there are quite # of powerful tools were built for real time usage.For example,

Facebook chat 100million requests are being handled

simpledb in AWS were implemented

Delicious bookmarking tool

sms component in TMobile

rabbitmq

couchdb

It has been tested in all sides in ATM AXD301 machine.

What erlang gives to us?

It is the concurrent programming language. It derives many features from various type of programming language to be focused o concurrent application implementation effectively.

So, Erlang guts are

No shared memory

Functional programming language

immutable and pattern matching

No sharing

There is nothing about shared memory in erlang virtual machine.The process communication is handled through message passing in asynchronous way to avoid synchronization overhead.So, it is the server side programming language, where you can derive the needful specific behavior(event handler, finite state machine) from erlang library to implement your server.

immutable and pattern matching

variables can’t be reassigned.The value of the variable can’t be changed.It has the feature called pattern matching to extract the data from the clause.

Functional programming language

Dynamic type system is used in erlang. Functional programming features are the core in erlang.

useful links

10min python: dis

what is dis?

dis is the disassembler. It shows to you how the python interpreter executes your python code in human readable format.

why do we need it?

To understand and optimise your python code to make it easier to the world.

how it works?

There is an inbuild module called dis which has the job and does it.It just reads the compiler understandable code(means byte code) and converting into mneumonics which is the cpu understandable language.

in this above example, first column is line no of our python code statements.Second column is the neumonic instraction address position(I think but not sure), third column is the mneumonic instructions for the cpu, last column is human understanble format mapping between python code to assembly code

I ordered this book last week for Rs 399. I got it delivered by today. Initially, i felt little disappointed when i took first look of the book.Since, it has very less no of pages for the cost Rs 399.I started it, it went very well, everything was explained in crispy manner, no less in clarity. All flavors are mixed in the manner which will make strengthen the understanding of getting things done.

I realized in the midst of the chapter that I was wrong on my initial disappointment. 😦

I would say shortly, This book is like a “ABCD for the software programmers”. Everyone should have passed this understanding, before taking their weapons. I am happy at least I am getting understand right now. Thank you Shakthi Kannan for this wonderful piece. I am sure, this creature will make more creatures in open source industry.